Apple is not fighting jailbreaking, at least not with more than token efforts to appease people like AT&T and other carriers. All iPhones revisions out there can be jailbroken and can be unlocked and there is a huge number of iPhones out there in countries that don't even have an official iPhone carrier.

Apple collects a nice sum of money for every iPhone sold and does not care whether that was carrier subsidized and whether said carrier now makes a loss due to the fact that the phone was jailbroken and unlocked and used one a different network.